Oral motor function

The mouth is one of the parts of the body capable of the most finely controlled movements. Oral motor function is an umbrella term for the ability of the various structures around the mouth to move in coordination. It has four main roles.

• Eating: Babies suck at the breast or from a bottle, and as they grow, they bite, chew, and crush food. The mouth's work includes the tongue gathering food and moving it toward the throat.
• Swallowing: The first stage of swallowing takes place inside the mouth. The tongue contacts the palate and pushes the food bolus backward. The throat and esophagus then take over (Dysphagia).
• Speaking: Speech sounds are made by bringing the lips together and separating them, placing the tip of the tongue against the upper gum ridge, and raising and lowering the palate. In Korean, the sounds “m” and “b/p” are made with the lips, while “n” and “d/t” are made with the tongue tip. The ability to produce precise speech sounds is called articulation.
• Breathing and facial expressions: Keeping the mouth closed and breathing through the nose also depend on the strength of the lips and tongue. The cheek and lip muscles are used in expressions such as smiling and frowning.

Several cranial nerves share responsibility for oral motor function. The trigeminal nerve controls the chewing muscles (Trigeminal nerve), while the facial nerve controls the lips and cheeks. The Glossopharyngeal nerve and vagus nerve control the palate and throat, and the hypoglossal nerve controls tongue movements. Because several nerves work together even in a single action, dysfunction in just one area can make eating or speaking movements less coordinated overall.

The main muscles involved include the Masseter muscle and temporalis, which close the lower jaw; the orbicularis oris, which brings the lips together; and the intrinsic and extrinsic tongue muscles. The muscles above the hyoid bone pull the hyoid bone and larynx upward during swallowing, while the muscles below it bring them back down to their original positions afterward (Hyoid bone).

Babies are born with reflexes for sucking and swallowing milk. Alternating between sucking, swallowing, and breathing during feeding is also a natural process. Around 6 months of age, as complementary foods are introduced, babies gradually learn to chew. At first they mash food with their tongues, then press it with their gums, and later chew with their molars using side-to-side rotary movements. As they learn to drink from a cup, use a straw, and begin speaking, their mouth movements become increasingly refined.

The pace of this process varies from child to child. However, if a child continues to drool for a prolonged period, frequently spits out food, often coughs or chokes during feeding, or has persistent difficulty with pronunciation, an assessment by a speech-language therapist, occupational therapist, or pediatrician is an option.

Integrative Manual Therapy (IMT) considers function around the mouth together with neck posture. It explains that when a forward-bent head posture is sustained, the flexor muscles at the front of the neck remain tense and the muscles around the hyoid bone remain stretched. From this perspective, difficulty swallowing and articulating speech commonly occurs in this state. *Integrative Manual Therapy for the Upper and Lower Extremities* describes how strain-counterstrain techniques applied to the anterior cervical region may be used to support speech and oral motor function (Advanced Strain and Counterstrain).

You can read more about the concept that the neck and jaw are connected through nerves and muscles and influence each other in Cervicomandibular relationship.

• Chewing on only one side, tiring easily, or having an aching jaw during meals may be a sign that the chewing muscles are being used disproportionately on one side.
• On some days, speaking for a long time leaves the jaw or neck tired and makes the voice crack.
• If your mouth often falls open while breathing, your lips and tongue may be weak, or your nose may be blocked (Mouth breathing).
• On days when you spend a long time at the computer, your head may move forward, and you may feel as though something catches in your throat when you swallow (Forward head posture).

• Chew slowly, using both sides: Avoid putting too much food in your mouth at once, and try alternating between the molars on each side.
• Adjust your posture: Gently tucking your chin and straightening your back at the dining table makes swallowing easier. Eating or drinking while lying down can cause coughing or choking.
• Keep your mouth comfortably closed: A comfortable resting position is with the lips lightly closed and the tongue resting against the palate.
• Practice speech sounds: Looking in a mirror and clearly making sounds that bring the lips together, such as the Korean “b/p” and “m,” provides practice using the lip muscles.
• Consult a professional: You can read more about methods for training the balance of the muscles around the mouth in Orofacial myofunctional therapy.

If you frequently choke or cough whenever you swallow food or water, your voice becomes wet-sounding after meals, you lose weight, or your speech suddenly becomes slurred and one corner of your mouth droops, you need to be assessed at a hospital. Sudden changes in particular may be an emergency. In these situations, consult a medical professional first rather than receiving manual therapy.